Lead sulfide (PbS) quantum dots are attractive candidates for optical refrigeration due to the tuneability of their band gap as a function of size and the resulting quantum confinement. We focus on the simple and straightforward method of synthesis of PbS NPs coated with zein protein with well-defined morphologies which show remarkable pH responsive behavior and excellent photo physical properties. The synthesis of PbS NPs in the presence of zein depicts a fine shape control effect as indicated in TEM images. At 0.4 %, zein produces nanocubes of ~ 42 nm which convert into spheres of almost equal dimensions with 0.2 % and 0.1 % zein. Since all reactions contain equal amount of precursor with identical conditions except the amount of zein, the shape transformation from nanocubes to spheres is mainly due to the decrease in the amount of zein from 0.4 to 0.2 %. The presence of protein coating makes the NPs bioactive and pH responsive. An increase in the pH systematically increases the absorbance of PbS NPs with a significant red shift which is simultaneously shown by remarkable color change in the solution from light grey with orange tinge to dark brown. These photo physical properties may have implications on laser cooling and it will be discussed.

Date Published: 27 February 2015
PDF: 7 pages
Proc. SPIE 9373, Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling XII, 93730M (27 February 2015); doi: 10.1117/12.2078279

Published in SPIE Proceedings Vol. 9373:
Quantum Dots and Nanostructures: Synthesis, Characterization, and Modeling XII
Diana L. Huffaker; Holger Eisele, Editor(s)